1. Field of the Invention
The present invention relates to a drive control apparatus of an electric synchronous machine having a field winding.
2. Description of the Related Art
An electric synchronous machine is composed of a three-phase armature winding and a field winding. The armature winding has three phase-windings which are supplied respectively with driving phase-current iu, iv and iw. Voltage Vf is applied across the field winding to supply field current if, thereby generating field magnetic flux.
The field current may be controlled in a vector control process using d-q rectangular coordinate axes with the magnetic field component set on one of the axes.
A synchronous electric machine disclosed in JP-A-9-74607 is mounted in a parallel hybrid vehicle together with an engine and an infinite variable-speed transmission. The synchronous machine is not used when the vehicle is driven at a constant speed but is used only when the vehicle is in a transient operation such accelerated or decelerated.
Preferably, the field current should be supplied only when the vehicle is accelerated or decelerated to improve the power efficiency of the hybrid vehicle. However, in the conventional drive control apparatus can not increase the field current immediately when driving power or battery charging energy of the synchronous machine is needed during the transient operation. If field voltage Vf is applied to the field winding, counter-electromotive force ef is generated as expressed in the following expression. EQU ef=Lf (dif/dt), [E1]
where Lf is an inductance of the field winding.
The counter electromotive force ef impedes increase in the field current if and, in turn, increase in magnetic flux .phi.f.